The invention relates to a stepping mechanism for rotary motions.
Stepping mechanisms are known for a plurality of uses. In this connection, it is often desirable to have available a simply functioning stepping mechanism which is miniaturizable to a high degree, which can be stepped at high speed, and which occupies exact stepped positions. From DE-PS 33 17 583 there is known, for example, a rotary nozzle arrangement, also miniaturizable to a high degree, which can be used for the control (e.g. steering) even of small-caliber shells. This rotary nozzle arrangement comprises a rotary nozzle body which is driven by the propellant stream, e.g. of a gas generator, continuously, at a high speed. The propellant stream issues from a thrust nozzle. The rotary nozzle arrangement is mounted in a missile so that the propellant stream is blown out approximately radially to the missile casing and hence exerts a steering force on the missile. The direction of the propellant stream can be defined with the aid of a brake which acts on the rotary nozzle body and can retain the latter in any desired position. The entire rotary nozzle arrangement can be miniaturized so that its diameter is in the millimeter range. Instead of using a brake for the retention of the rotary nozzle arrangement, also a stepping mechanism would be suitable which presets certain positions for the rotary nozzle body.
A stepping mechanism is known from U.S. Pat. No. 4,463,921. With this stepping mechanism, the position of a gas distributor is adjusted. The gas distributor communicates with blow-out ports at the circumference of the casing of a missile and through which a propellant stream of a gas generator is blown out in different, approximately radial directions for the steering of the missile. This known stepping mechanism, however, is relatively expensive as to design and is not miniaturizable to the desired degree.
It is the object of the present invention to provide a stepping mechanism for rotary motions which is miniaturizable to a high degree and which offers high setting speeds combined with the possibility of exact positioning.
According to the invention, the objective is achieved through a novel brake which is engaged and displaced by a wheel-side stop of a switching wheel prior to the rest position of the switching wheel, as will appear.
In the stepping mechanism of the invention, a continuous drive of the switching wheel is necessary. This continuous drive can take place e.g. by means of the above-mentioned rotary nozzle arrangement if the rotary nozzle body is connected coaxially with the drive shaft of the switching wheel. The continuous drive provides a very high stepping speed in the operation of the stepping mechanism. For the switching wheel, which carries at least one wheel-side stop, an escapement mechanism with at least one pawl is provided. To obtain exact positioning of the switching wheel and an optimally delayed entry of the switching wheel into the respective stepped position, there is provided, in the region of the pawl, a brake with a run-up edge on which the wheel-side stop of the switching wheel runs up before its entry into the final stepped position. The brake is thereby displaced and the switching wheel is delayed in entering into the final stepped position. Preferably, the braking action, i.e. the force needed to displace the brake, is adjustable, e.g. by means of compression springs or by magnetic pressing, in that the brake is arranged between the pawl and a magnet. Depending on the strength of the magnet, the brake will be pressed more or less against the magnet or a friction disk, and the braking force is thereby adjustable.
To obtain a dynamically balanced operation of the stepping mechanism, the escapement mechanism preferably comprises two pawls located on opposite sides of the switching wheel and also two brakes. The pawls, as well as the two brakes can be formed by a rocker, both of which are pivotable about a common axis. The axis here lies in the center between the pawls or the run-up edges, respectively. As a result, practically no imbalances occur during operation.
The escapement mechanism can be brought into the required position by an external actuating device, but it is advantageous to utilize for this purpose, at least in part, the drive force for the switching wheel, which is available anyway. The wheel-side stops and the pawls are formed so that, during the abutment of a wheel-side stop, a force acts on a pawl which force pressurizes the pawl in the direction of release of the wheel-side stop. A releasable holding device must then also be provided for the pawl. If the pawl is thereby released, it is pushed away by the wheel-side stop, the wheel-side stop being released. If then, e.g., two pawls are provided jointly on a rocker, the other pawl can thereby be brought into a position in which a wheel-side stop is retained in the next stepped position. The actuation of the pawl by the drive force can be further supported by a compression spring.
On the same principle also, the brake can be positioned accordingly by the switching wheel, in particular, if the brake is designed as a rocker with two opposite run-up edges. To obtain an exact positioning of the pawls, fixing means may be provided in which the pawl is retained in the desired two positions in each instance. Such fixing can occur for instance, by means of lock balls.
The masses to be moved in the stepping operation of the stepping mechanism are very small, so that, on the whole, a stepping mechanism with small inertia is made possible.
It is also an objective of the present invention to provide a straight forward design for a stepping switch, of the type described above, which functions with few component parts.
This objective is achieved according to a further embodiment of the present invention, by providing two connecting links, a pawl link and a clamping link, which move in simple shifting movements, into respective two switching positions, perpendicular to the axis of rotation of the rotary operating mechanism. This provides the use of simple bearing and guide means for the connecting links, for example with the use of pins and slotted holes. The spring supported movement of the pawl link is accomplished with the help of an annular spring, which encircles both connecting links and abuts against only one of the connecting links, at any one time, on opposite sides in the area of the guide means. This annular spring is deformed by the clamping link, which is actuated by the ratchet wheel, and is thereby tensioned, so that it exerts a force, in the direction of the axis of rotation of the rotary operating mechanism, on the pawl link, which is retained in one switching position. If the pawl link is released, it is then shifted by the annular spring into the other switching position, in which it now abuts against the annular spring on the opposite side. When the ratchet wheel is rotated further, the clamping link is simultaneously pressed into the other switching position, so that it again lies on the now other side of the annular spring, and tensions it once more with deformation. This exchange cycle repeats itself.
In the case of the stepping switch, according to the further embodiment of the present invention, it is not essential that any self-arresting action occurs during the operation of the escapement mechanism. On the contrary, the pawls and the end stops on the ratchet wheel can be made conventionally, so that self-arresting action occurs. Of course, a functioning without self-arresting action is also possible, whereby as in the case of the above described embodiment of the invention, the shifting of the pawl link into the other switching position, at the time, is supported by the ratchet wheel.
The escapement mechanism of the stepping switch according to the further embodiment of the invention, features only three simple component parts, namely the two plate-shaped connecting links, as well as an annular spring. These parts are simple to manufacture, so that, to a great extent, the stepping switch can be miniaturized.
The invention will now be described in greater detail in the following detailed description with reference to the accompanying drawings.